The invention relates to a heat exchanger for a heating system with integrated fuel cells for the production of electricity and also to a system with a heat exchanger of this kind.
A heating system with integrated fuel cells for the production of electrical and thermal energy is known from EP-A-0 818 840, wherein the operator of the heating system, the “local energy user”, can cover his needs regarding the named forms of energy, at least in part. This heating system includes an additional burner. Various possibilities are described as to how a maximum amount of thermal energy can be given in a heating system which includes room heating and/or process water heating, from the primary energy which is made available in the form of a gaseous fuel. For economic reasons, various measures have been put forward and realized to further simplify the known procedure, wherein one has continued to strive for an ideal utilization of the primary energy. In the method known from EP-A-0 818 840 pure water is needed to reform the fuel. One measure for the simplification of this method was the treatment of the fuel, which can also be present in liquid form, by means of a reformation process with partial oxidation. The partial oxidation renders superfluous the expensive necessity of making available pure water as an additional educt during reforming.
Further measures are a) to arrange a heat store between the system for the production of electrical and also thermal energy and the local energy user and b) if necessary to produce an excess of electrical energy which is given off to a grid of the public electrical energy supply. In the production of an excess of this kind an excess of thermal energy often arises as well which exceeds the current requirement of the local energy user. This thermal energy can be stored temporarily in the heat store. Electrical energy is only produced to excess until the heat store has been fully loaded. An excess of thermal energy can also arise if the local energy user requires a relatively large amount of electrical energy on occasion. A storing of the excess heat is also advantageous in this case.
The transport of heat from the heating system with integrated fuel cells to the heat store has to take place using suitable heat transport mediums. In this arrangement a heat transport is to be carried out to the heat store and/or to the local energy consumer from two exhaust streams, namely from an exhaust stream of the fuel cells and from an exhaust stream of the additional burner. Two independent variables are given by the two exhaust streams, the ranges of which extend respectively between zero and a maximum value. A liquid heat transfer medium, in particular water or an oil, is advantageously provided for the heat transport, with which the heat can be transported to the local energy consumer.